johnsmachines

machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment. I read every comment and respond to most.

Tag: casting chess pieces

Walking Dead Chess Men

Today I poured 3 cylinders of brass to make 12 chess pieces. 8 pawns and 4 rooks. It was a total failure.

A model engineering friend had donated 3.3kg of brass, in the form of spent cartridges.

First a wash in hot strong detergent..
Meanwhile the cylinders were going through drying and baking cycles
and approximately an hour before the cylinders were finished, the cartridges were melted at 1070ºc….that is hot!
then poured. All straightforward so far. The egg yolk in the middle is actually hot fluorescent orange as in the previous picture.
but after removing the investment medium, the brass figures are disappointing. Poor surface detail. Left over brass melt ingots in the background.
… lots of surface bubbles, and voids. They do remind me of walking dead zombies.
and the rooks are similarly disappointing, with poor surface detail, voids and bubbles.

This is the first pour which I have done in 3-4 months. It was ambitious, requiring 3.25kg of investment powder, and 3 large cylinders. But these pieces will all be redone, with new 3D prints, and recasting. The failed pieces will be remelted.

I think that the main problem was that the investment mixture which I painted onto the prints was too thick, and did not penetrate all of the surface features. And the painting was not adequately thorough, leaving bare areas which predisposed to bubbles.

And the main bulk of the investment mixture was too thick. I did mix it a bit longer than usual because of the volume involved, and I did notice that it seemed more viscous than usual, and when vacuumed, the bubbles never really stopped coming.

The voids occurred mainly at the bottom of the cylinders, which indicates I think, a need for ventilation tubes. I had stopped using those for bronze pours, but maybe for brass they are necessary.

So, at this moment I feel that it was a wasted day. But I have learned some things, and have a plan for the next pours.

And I was very satisfied with the quality of the brass from the cartridges. Hopefully that will continue as a source.

Casting Brass Chess Pieces- 2

OK. So I hope that you saw the pics of 3d printing the pieces, then making some trees using the PLA pieces, wax parts, steel cylinders etc.

Today I mixed the water and Jewellers Investment powder, and poured the mixture into the cylinders. This was the largest volume of mixture that I had attempted.

1.5kg water, and 4.25kg of investment powder.

I keep a record of every mixture, every metal pour.
The rubber tub is for the mix. The vacuum pump and container are to extract as much air from the mixture as possible. The pump is 1hp.
Making the mixture, degassing it, and pouring it, is a tense time, so no pics. This shows the scales for measuring the weights of the water and investment powder. I use some old beaters to do the mixing. The degassing. Then pouring into the cylinders.
After an hour or two, the rubber base is removed, showing the trunk of the wax tree, and the metal pouring funnel.



The cylinders are placed in the potter’s oven. I have set the timer to commence the burnout at 6am tomorrow, at 250ºc. The funnel is upside down, so any melted PLA of wax will run out onto the bench. I leave a slight gap in the door closure. I will arrive at about 9am and complete the burnout at temps up to 750ªc, then do the metal melt and pour 4-6 hours later. Wish me luck!